Conductance values of alkanedithiol molecular junctions

We study the electrical conductance of octanedithiol molecular junctions using a mechanically controllable break-junction setup. The stability of the system allows control of whether the electrodes get into contact before each new molecular junction formation or not (contact and non-contact modes). We find three characteristic conductance values for octanedithiol. Well-defined peaks in the conductance histograms at multiples of 1.2 × 10 −5 G 0 suggest that this value corresponds to the conductance of a single molecular junction conductance. Reproducible features are also observed at 4.5 × 10 −5 and 2.3 × 10 −4 G 0 . The first value has the strongest statistical weight, whereas the second is only observed in the non-contact mode. We propose that these two values reflect the formation of several molecular junctions in parallel between the electrodes.